Molded pulp article



Nov. 7, 1967 R. F. REIFERS 3,351,255

MOLDED PULP ARTICLE Original Filed June 16. 1964 3 Sheets-Sheet l Nov. 7, 1967 Original Filed June 16, 1964 R. F. REIFERS MOLDED PULP ARTICLE 3 Sheets-Sheet 2 Nov. 7, 1967 R. F. REIFERS 3,351,266

MOLDED PULP ARTICLE Original Filed June 16. 1964 3 Sheets-Sheet 3 HVVE$HYDR MCHARD F REWERS United States Patent ABSTRACT OF THE DISCLGSURE The present disclosure relates to a molded pulp article, the peripheral end portion of which is free to flash without having been subjected to a flash removal operation. The peripheral end portion corresponds to a plurality of petal-like projections each of which has a triangular .cross section. The apex of which ends at the extreme edge of the pulp molded article. These projections having a triangular cross section are formed by molding the pulp under a deckle ring having undercut portions and then blowing the article from the forming mold: the deckle ring performs a wiping action on the projections as the article is blown from the mold and this deforms and/or removes the flash from the edge of the article.

This is a divisional application of my copending application Ser. No. 375,512 filed June 16, 1964, now Patent No. 3,306,813.

The present invention relates to pulp molding and more particularly to a pulp molded article free of flash and having a gripping peripheral edge.

Flash tends to form on some areas of pulp molded articles, particularly the trailing edges thereof, because the stock tends to pile up on one part of the article or it sticks to the deckle ring. Until the present time, it has been necessary to utilize a separate deflashing step or operation in the formation of pulp molded articles. Articles formed without such a deflashing step have not been commercially suitable since they often have unattractive flash deposits extending from the peripheral edges thereof. No molding method known up to the prior time has utilized any means of eliminating such flash except by carrying out some type of an additional deflashing step to either effect deflashing or an additional molding of the flash containing edge of the article. At any rate, some type of additional operation, step, or molding position has been necessary in the prior art, all of which increased the expense of forming pulp articles.

Many pulp molded articles, such as trays utilized in the packaging of food products, are used in conjunction with an overwrap film of some type, which film maintains the food product in position within the pulp molded tray. Most often such films comp-rise transparent plastic. Until the present time, it has proven difiicult and expensive to provide additional means to secure the overwrap film to the pulp molded tray.

It is therefore an object of the present invention to provide a pulp molded article obviating the diiiiculties of the prior art, such as those indicated above.

It is another object of the present invention to inexpensively provide a pulp molded article which is commercially attractive, and provide means for gripping an overwrap film.

It is another object of the present invention to provide a highly satisfactory pulp molded article without flash on the decorative edges and provide such article with exceptionally clean edges.

It is another object of the present invention to provide a distinct and well defined decorative edge on a pulp molded article which is essentially flash free and which article is exceptionally simple to manufacture.

' upper edge 16, a lower edge 18' 3,351,266 Patented Nov. 7, 1967 These and other objects and the nature and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial plan view showing an article in ac cordance with the present invention;

FIGS. la and 1b are partial sectional views taken along lines 1a1a and 1b1b, of FIG. 1;

FIG. 2 is a sectional view taken through a mold in accordance with the present invention;

FIG. 3 is a partial sectional view on an expanded scale similar to FIG. 2;

FIG. 4 is a partial plan view of an edge forming device in accordance with the present invention;

FIG. 5 is a partial bottom view of the device of FIG. 4;

FIG. 6 is a sectional view taken along lines 6-6 of FIG. 5;

FIG. 7 is a sectional view taken along lines 77 of FIG. 5;

FIG. 8 is a sectional view taken along lines 8-8 of FIG. 5;

FIG. 9 is a partial plan view similar to that of FIG. 1;

FIG. 9a is a partial sectional view taken along line 9a-9a of FIG. 9;

FIG. 10 is a plan view of another article in accordance with the present invention;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 10; and

FIG. 12 is a detailed sectional view taken along line 1.212 of FIG. 10.

FIG. 1 shows, as one example of a pulp molded article formed in accordance with the present invention, a cake circle Iii, having scalloped-like projections 12 extending from the peripheral end portion 14 thereof. In the cake circle 10, the extensions 12 serve to provide the cake circle with a pleasing decorating edge.

The scalloped-like extensions 12 of the cake circle 10, besides projecting outwardly from the peripheral end portion 14, may also extend at least in part out of the plane of the cake circle such as shown in FIG. la, in a manner similar to the petals of a flower. As seen in FIG. 2, the article is not molded with the extension 12 projecting out of the plane, but such projection out of the plane (or flower petal effect) may be formed during removal of the article from the mold.

The extreme peripheral portions of the cake circle 10 are defined by an upper edge 16 and a lower edge 18. The upper edge 16, depending on the thickness of the article in relation to the extension forming portions of the mold, approaches a circle in configuration while the lower edge 18 comprises either the sole or the major defining edge of the extensions 12. Each extension 12 in addition has a sloped facing surface 20 which is essentially crescent-shaped with a maximum dimension shown in FIG. 1a and which facing surface 20 forms the hypotenuse of the triangle formed by the cross-section of such extension 12.

While the extensions 12 are shown in FIGS. 1, 1a, 9 and 9a to be essentially scallop-like, in shape, it is understood that the invention is not limited to the production of extensions of this particular shape. Thus, as viewed in FIG. 1, the extensions 12 may project like saw teeth. The projections may also be of nonuniform size and spacing. In addition, unlike the extensions 12 shown, the extensions may be of uniform shape along the length and thus not vary continuously along their length.

The extensions 12 of the cake circle 10 of FIG. 9 are similar to the extensions 12 of FIG. 1 and have an and a sloped facing surface 20'. As seen by a comparison of FIGS. 1 and 9, however, the extensions 12' of FIG. 9 are smaller than the extensions 12 of FIG. 1 with the consequent result 3 that edge 18' is shorter and each surface 20 smaller than the respective edge 18 and surface 20* of FIG. 1. Cornparing FIG. 9a with FIG. 1a, it is seen that the cake circle 10' of FIG. 9 does not have its extensions 12 projecting out of its plane in a flower petal eflect.

FIG. 2 shows a mold 22 in accordance with the present invention for producing the cake circles 10* or 10'. The mold 22 comprises a backing plate 24 which has across its front a molding surface 26 which is permeable to the passage of air and water. Generally, and as well known in the art, such a permeable molding surface 26 will take the form of a molding screen. The mold 22 contains hollow portions 28 and holes 30 which pass from the hollow portions to the permeable molding sur face. The mold is supported, generally for rotary passage through a pulp slurry containing molding vat, by a hollow spoke 32 such as is well known in the art. Means are pro vided (not shown) for both applying vacuum and positive fluid pressure through the hollow spoke 32, the hollow portions 28, and the holes 30 to the permeable molding surface.

During the molding operation, in a manner well known, the mold 22 is passed through a pulp slurry at which time vacuum is applied through the mold to effect deposition of the pulp deposit 10 or 10. Similarly, after completion of the deposition, the article 10 or 10" is removed from the mold by blowing air through the permeable molding surface 26 thereby forcing the deposit from the molding surface.

It is often desirable to use, in the construction of a mold 22, a peripheral deckle ring 34- which is held in place by screws 36. The purpose of the deckle ring 34 is to form a relatively smooth peripheral surface on the molded article 10. In addition, if the permeable molding surface 26 is a molding screen, the deckle ring 34 may be used to anchor the screen in place over the front surface of the backing plate 24. In the present invention, the deckle ring 34 is provided with undercut portions 38 about its periphery, which undercut portions effect the molding of the extensions 12 and 12.

FIGS. 2 and 3 show the mold shortly after it has been removed from the pulp slurry after deposition of the deposit 10, but prior to removal thereof. As is seen, the cake circle 10, while on the mold, is essentially planar and at least the peripheral end portion 14 of the deposit lies in a single plane. In addition, it is seen that the extensions 12 lie beneath the undercut portions 38 of the deckle ring 34.

In accordance with the present invention, the pulp deposit 10 is removed by blowing air through the molding screen 26 to force the deposit 10 from the mold. Because the extensions 12 of the article extend a substantial distance beneath the undercut portions 38 of the deckle ring, the article cannot readily escape from the mold. However, sufficient air pressure is used to force the article out of the mold regardless of the undercut portions 38; this causes the undercut portion 38 to exert a greal deal of pressure on the extension 12 formed thereunder and as the article escapes from the mold the undercut portion provides a wiping action along the surface of the extension 12. This, in turn, causes the extensions 12 to deform in the manner shown in FIG. 1a. In addition, the article 10, immediately after removal from the mold, is essentially free of flash along its decorative edge.

FIG. 3 shows an expanded view of another mold in essentially the same position as that of FIG. 2. In the mold of FIG. 3, however, an opposing pressure mold 40 is used to smooth the upper surface of the article prior to the removal step.

The same procedure as described above is utilized in the formation of the article 10' further utilizing the same stock and the same processing variables. In this case, however, the extensions 12' extend only a short distance beneath the undercut portions 38 of the deckle ring. As in the formation of article 10, suflicient air pressure is used to force the article out of the mold regardless of the undercut portions 38 and as the article escapes from the mold the extensions 12 are deformed or flexed in a manner similar to that shown in FIG. 1a. However, due to the small size of extensions 12, the amount of escape deformation is minimal and the extensions 12 return to their normal position as shown in FIG. 9a. This is due to the fact that the pulp fibers are molded in a correct position and have no elastic memory to that position to which they will return unless their elastic limit is exceeded during escape (such as in the removal of article 10). Whether the elastic limit is exceeded as the extension escapes the undercut portion of the deckle ring depends on, besides the depth of the undercut, a number of other variables, such as the wood fibers used in the stock, the fiber length, the density of the mat or deposit, the thickness of the mat, the processing variables, etc.; therefore there is no specific undercut depth which is a transition point on one side of which is produced the flower petal extensions 12 and on the other side of which is produced the flat extensions 12. Like the extensions 12, however, the extensions 12 are also substantially free of flash along the decorative edge after removal of the article 10' from the mold.

It is believed that the reason the articles produced are free of flash is that the over-hung portions of the deckle ring above the undercut portions tend to keep excess pulp or flash remote from the final true edge of the article. Should any flash be formed at all, it would be in an area not normally seen by the customer.

FIGS. 4 to 8 show the details of construction of the deckle ring 34 used to form the scallop-like extensions 12 of the article of FIG. 1. Each undercut portion 38, 38 and 38 are of uniform size and are spaced uniformly apart, with the starting point 42 of one undercut portion coinciding with the ending point of the previous undercut portion (although at the point 42 itself there is no undercut). The product configuration produced at point 42 lies between extensions 12 and corresponds to an end portion 14 as shown in FIG. 1b, and under ideal molding conditions the deposit will abut the vertical wall 37 of the deckle ring 34 as shown in FIG. 6 during the molding.

Under perfect molding conditions (quiet and thin stock), the wet stock deposit would approach the formation shown in FIGS. 6-8. In actuality, the stock at the upper edge 16 will tend to fall back somewhat from the deckle walls 37 and 38 as the wet pulp deposit contracts from a thick mat to a thin mat as the deposit increases in density during application of vacuum after removal from the pulp slurry. In FIG. 7 it is seen that an undercut portion 38 is intermediate in size as it continuously varies in size along its length growing to a maximum at the location through which section line 8-8 is taken designated by the numeral 44 as shown in FIG. 8. While the crosssection of the undercut varies in size along its length, it nevertheless retains its triangular cross-section. The deckle ring edge 48, which is complementary to the product edge 18, thus varies continuously in position with regard to the inner peripheral wall 37 of the deckle ring, which is circular, and which is complementary to the upper edge 16 of the product.

As seen in FIGS. 6, 7 and 8, as well as FIGS. 1a and 1b, the upper peripheral edge 16 of the article 10 will always be circular so long as the thickness of the article is at least as great as the maximum height of the undercut portion 38 shown in FIG. 8. If, however, a thinner article is produced, then the upper peripheral edge 16 of the article will also oscillate in a manner. similar to the lower peripheral edge 18 except that its variations will not be as great.

When other articles are formed, such as trays, the extensions 12 also serve as friction gripping means about which an overwrap film can be more securely anchored than to a smooth peripheral edge. It is to be understood that, while a cake circle 10 is shown, any pulp molded 5 article, particularly a tray, can be formed having such or similar extensions 12 which will serve the above functions.

FIGS. 10l2 show a food tray 50 having a horizontal scalloped peripheral flange 52, along with the conventional horizontal bottom wall 54 and the four inclined side walls 56. As shown in FIG. 11, such a tray 50 may be packed with foodstuff, such as fruit 58, and then covered with a transparent plastic sheet 60 which is heat shrunk about the peripheral flange 52 at 62. As can be seen in FIG. 12, which is a section taken between two scallops, the plastic sheet 60 Will shrink to conform to the scallops and this will assist in anchoring the plastic 60 to the tray 50.

By carrying out the teachings of the present invention, it has been found that the pulp molded articles immediately after removal from the mold are without the flash which is usually present around the decorative peripheral edges of most molded pulp articles. In addition, the seallop-like edges produced, besides providing an attractive and decorative package, are also extremely useful in anchoring overwrapping films.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

What is claimed is:

1. A pulp-molded article comprising:

a body portion;

an end portion peripheral to said body portion, said end portion having a plurality of projections extending outwardly therefrom and ending in an edge which forms the extreme edge of said peripheral end portion, said peripheral end portion being essentially free of flash without having been subjected to a distinct flash removal operation, each said outwardly extending projection having a variable thickness corresponding to a maximum at the location closest to said body portion and a minimum at said extreme edge to provide an essentially triangular cross section the apex of which corresponds to the extreme edge of said peripheral end portion.

2. An article in accordance with claim 1 wherein said projections are disposed in part out of the plane of said peripheral end portion.

3. An article in accordance with claim 1 wherein said projections are of relatively uniform size and spacing.

4. An article in accordance wit hclaim 1 wherein the cross-sectional configuration of each said projection varies along its length.

5. A molded pulp tray in accordance with claim 1 comprising a bottom wall, a side wall extending upwardly and outwardly from said bottom wall, and a peripheral flange extending downwardly and outwardly from said side wall, said peripheral end portion forming the outer portion of said flange.

6. A tray in accordance with claim 5 further comprising a plastic sheet heat shrunk about said peripheral flange and conforming to said outward projections.

7. A cake circle in accordance with claim 1 comprising a bottom wall surrounded by said peripheral end portion, and a plurality of concentric ridges upstanding from said bottom wall.

References Cited UNITED STATES PATENTS 2,041,537 5/1936 Frost 229-2.5 X 2,109,955 3/1938 Carson 229-2.5 X 2,975,931 3/1961 Harrison 229-2.5 XR 3,092,246 6/ 1963 Harrison et al 206-45 .33 3,153,505 10/1964 Bessett 229-43 DONALD F. NORTON, Primary Examiner. 

1. A PULP-MOLDED ARTICLE COMPRISING: A BODY PORTION; AN END PORTION PERIPHERAL TO SAID BODY PORTION, SAID END PORTION HAVING A PLURALITY OF PROJECTIONS EXTENDING OUTWARDLY THEREFROM AND ENDING IN AN EDGE WHICH FORMS THE EXTREME EDGE OF SAID PERIPHERAL END PORTION, SAID PERIPHERAL PORTION BEING ESSENTIALLY FREE OF FLASH WITHOUT HAVING BEEN SUBJECTED TO A DISTINCT FLASH REMOVAL OPERATION, EACH SAID OUTWARDLY EXTENDING PROJECTION HAVING A VARIABLE THICKNESS CORRESPONDING TO A MAXIMUM AT THE LOCATION CLOSEST TO SAID BODY PORTION AND A MINIMUM AT SAID EXTREME EDGE TO PROVIDE AN ESSENTIALLY TRIANGULAR CROSS SECTION THE APEX OF WHICH CORRESPONDS TO THE EXTREME EDGE OF SAID PERIPHERAL END PORTION. 